Final Fantasy has been downhill ever since Enix merged with Square. If I recall, X-2, XI, XII, XIII, and XIV were all under Square-Enix. The only FF I've liked out of that bunch is XIII. Even then, I wouldn't say XIII is great. Good, but definitely far from the best FF in the series. I will say that VI and IX are the best in the series in my opinion.
I could never get into XI at all, so I didn't even bother looking into XIV. I'm not a big MMORPG person. I used to be with 2D MMORPGs years ago, but I never really play any MMORPGs now.